The innovations and related subject matter disclosed herein (collectively referred to as the “disclosure”) generally pertain to planar substrates and related systems, and more particularly but not exclusively, to curved substrates lying in a selected plane, with woven or knit substrates suitable for curved slide fasteners in which a wrinkle or wavy uneven surface on the substrate is reduced or eliminated being but particular examples of disclosed planar substrates.
A slide fastener can be attached to an apertured panel, as to open and close an opening portion of a bag, the front of clothes, and/or a trouser fly. A curved slide fastener, in which a fastener tape (or substrate) thereof is curved at a predetermined curvature along a longitudinal axis of the slide fastener in a horizontal direction (e.g., “in plane”) with respect to a major surface (e.g., the tape surface) thereof, is sometimes desirable to open and close a curved opening. Conventionally, warp yarns of a fastener tape running linearly (e.g., longitudinally) in parallel with each other in a weaving direction or a knitting direction are substantially inelastic. Thus, adjusting yarn tension in the weaving direction or the knitting direction of a conventional fastener tape, as by attempting to bend or curve the fastener tape horizontally with respect to the tape surface, causes one or more of the warp yarns (e.g., radially inward warp yarns) to buckle, causing a wavy surface extending out of plane relative to the planar surface of an undeflected, at-rest fastener tape.
With conventional, curved, slide fasteners, a plurality of juxtaposed notches arranged lengthwise (e.g., longitudinally) of the linear substrate have been cut into the substrate to overcome such buckling. FIGS. 1 and 2 show an example of a conventional substrate for a curved slide fastener disclosed in German Pat. DE7122407U having notches 5 and 6. However, such post-production notching increases costs and reduces reliability of the substrate as conventionally knit or woven yarns are cut, substantially weakening the substrate and thus the slide fastener. For example, free-cut yarns can cause the substrate to fray.
Thus, a need exists for substrates suitable for curved slide fasteners (e.g., zippers) that do not require post-production notching of the substrate. As well, a need remains for notched substrates that lack free, cut ends of yarns.